WO1983003732A1 - Appareil d'identification de signaux numeriques a frequences multiples - Google Patents

Appareil d'identification de signaux numeriques a frequences multiples Download PDF

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Publication number
WO1983003732A1
WO1983003732A1 PCT/SE1983/000107 SE8300107W WO8303732A1 WO 1983003732 A1 WO1983003732 A1 WO 1983003732A1 SE 8300107 W SE8300107 W SE 8300107W WO 8303732 A1 WO8303732 A1 WO 8303732A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
selective
signals
receivers
receiver
Prior art date
Application number
PCT/SE1983/000107
Other languages
English (en)
Inventor
L M Ericsson Telefonaktiebolaget
Original Assignee
JÄRVFÄLT, Staffan
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by JÄRVFÄLT, Staffan filed Critical JÄRVFÄLT, Staffan
Priority to GB08409831A priority Critical patent/GB2135488B/en
Priority to NL8320091A priority patent/NL8320091A/nl
Priority to BR8307505A priority patent/BR8307505A/pt
Priority to AU14757/83A priority patent/AU1475783A/en
Publication of WO1983003732A1 publication Critical patent/WO1983003732A1/fr
Priority to DK559683A priority patent/DK559683A/da
Priority to FI841600A priority patent/FI841600A0/fi

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q1/00—Details of selecting apparatus or arrangements
    • H04Q1/18—Electrical details
    • H04Q1/30—Signalling arrangements; Manipulation of signalling currents
    • H04Q1/44—Signalling arrangements; Manipulation of signalling currents using alternate current
    • H04Q1/444—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies
    • H04Q1/45—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling
    • H04Q1/457—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling with conversion of multifrequency signals into digital signals

Definitions

  • the invention relates to an apparatus for identifying digital multi- frequency signals, the received signals being fed through a group fil ter to a plurality of selective receivers answering to the discrete frequencies in the expected input signals, the input signal to each o said receivers being multiplied by a coefficient from each of two set of coefficients, the first set being obtained from multiplying a sinu function of the frequency specific to the receiver by a weighting fun tion, the other coefficient being obtained by multiplication of said
  • the selectivity requirement for multi-frequency code (MFC) receivers is to a major extent determined by the requirement that operation for single tone may not occur.
  • the time interval for calculating the correc ⁇ tion must be about 30 ms. If an output decision is based on comparison of the calculated correlations mutually as well as with some fixed threshold value, the risk is great that a short pulse of single tone or of a MFC signal causes operation if solely a 30 ms interval is re- quired for approval. Furthermore, the release time will be long if the same set of coefficients and thereby the same time interval is used fo
  • a requirement according to the R2 specification is that simultaneous signalling in the send direction shall not affect the receiver. Fre- quencies which are used in signalling in the send direction must therefore be filtered away. If this is achieved with a group filter which is common to the selective receivers, the selectivity require ⁇ ment for these may be reduced considerably, not only because the effec from signals in the send direction is already eliminated at the input to the selective receivers, but also because the previously mentioned measure for protection against noise signals can be taken, since the mean value of the signal after the group filter can be calculated and a variable decision threshold obtained. This threshold is related to the total energy in the signal after the group filter, i.e. within the frequency band for .the expected signals in the receive direction.
  • each calculation interval for the correlations could be.reduced to 15 ms with the-afore mentioned measure for protection against noise signals, but the release time would still be close to 30 ms even if only one calculation inter— val with the absence of signal were to be recognised as release. No indication of whether a short interruption can have disturbed the corr lation calculation is obtained, which can result in that a single tone subjected to a short interruption is recognised as the presence of two adjacent MFC frequencies.
  • the invention proposes that such changes in the input signal to the receiver are monitored which constitute possible indications that a signal starts or ceases, and depending on what stage of the signalling the receiver "is in, calculation of the correlations is started or time monitoring for release is started. Th monitoring is carried out with a non-selective receiver which is zero set with such a time interval and has such time constants that its output signal at the termination of the interval is a measure, suffi ⁇ ciently accurate for the purpose, of the mean value of the input sig ⁇ nal during the time interval.
  • Figure 1 is a block diagram of a multi-frequency receiver in accordan with the invention
  • Figures 2a-2f illustrate the signal wave form in different parts of the receiver.
  • the multi-frequency receiver includes a digi ⁇ tal group filter 7, which filters away to a sufficent extent all fre ⁇ quencies outside the intended frequency range.
  • the re ⁇ DC contains six selective receivers .-.6 and two non-selective re- ceivers 17, 18 for controlling a decision process which generates an output decision on the basis of the output signals from both the se ⁇ lective and non-selective receivers and also decides the times for zero-setting and reading out from these receivers, as will be explaine more in detail.
  • the selective receivers each answering to one of the discrete fre ⁇ quencies in the expected input signals, are of a type known per se, in which the input signal at each sampling time is multiplied by two co ⁇ efficients, one from each of a set indicated by the blocks 10, 11.
  • the first set, symbolized by the input 8 in the selective receiver 1 has been obtained by the multiplication of a sinus function by a weigh ting function, and the ' other set symbolized by the input 9 of the re ⁇ DCver 1 has been obtained by multiplication of said sinus function, phase shifted ⁇ - , by the same weighting function.
  • the results of multiplication of the input signal and said coefficients are accumu ⁇ lated for the two sets individually (indicated by the blocks 12, 13), the contents of the accumulators being individually squared ( indica ⁇ ted by the blocks 14,15) and the squared results being summed ( indica ⁇ ted by the block 16).
  • this measure is equal to the squared amount of the discrete Fourier transform (DFT) of the input signal multiplied by the weighting function which determines the re ⁇ DCver selectivity.
  • DFT discrete Fourier transform
  • Such a selective receiver is already known, e.g. through the articles mentioned in the introduction. In each of the selective receivers the DFT is calculated for the discrete frequency to which the set of coefficients corresponds.
  • the signal from the group filter is subjected to an absolute amount formation and digital low- pass filtering in a recursive filter of a type known per se, but where the discharging time constant is suitably greater than the charging " time constant.
  • the decision threshold for the selective receivers is a function of the output signals from the non-selective receivers.
  • the value of the decision threshold for the selective receivers is -.calculated in the non-selective receiver 18 and the squaring circuit 25, said threshold being a measure of the input signal energy within the frequency band of the expected signals in the receive direction.
  • the time constant of the digital lowpass filter is selected to a value large enought for the variations of the envelope of an MFC sig ⁇ nal only having small effect on the decision threshold, but is not selected greater than that the decision threshold has time to attain a relevant value of the total energy of the signal from the group filter during the time of the calculation interval in the selective receivers.
  • the discrete Fourier transform of the input signa solely at the expected frequencies- of the input signal.
  • the selectivity will be so low that it is hardly wort ' b whil also to calculate the DFT for other frequencies than the frequencies halfway between the MFC signals, for the purpose of detecting noise signals. If the input signal is not stationary during a calculation interval, or if it is indeed stationary but contains other frequenci than those expected, the calculated values of the DFT do not give sufficient information about the input signal.
  • the problem in the la case is solved by the variable decision threshold.
  • the apparatus in accordance wi the patent claim is provided with a further non-selective receiver 1 which can be used to give a rapid and reliable indication when the si nal ceases.
  • the normal change of energy due to the periodic envelope must however not be recognised as though the signal were not steady. If the lowpass filter in the non-selective receiver 17 is zero-set with sufficiently short intervals, short interruptions can be discove nevertheless.
  • the period time of energy in the envelope of an MFC sig nal is at most 5 ms, while an interruption of up to 7 ms must not cau an interruption in the output decision information.
  • an interval of 4-5 ms between zero-settings is appropriate It is also appropriate to allow the interval to be a whole sub-multip of the interval for calculating the DFT, which is about 16 ms, i.e. 4 for 16 ms and 5 for 15 ms.
  • the non-selective receiver 17 is affected by the changes in the compo input signal level and controls the start of the calculating periods response to these changes, as indicated by the output 22. If the outp signal from the group filter (Figure 2a) exceeds a given threshold (level 1) there is a continued monitoring by the receiver 17 and bloc 19 during continuously repeated 5 ms intervals, according to the exam This threshold can be fixed or signal-responsive. If a sufficiently long time has passed (Figure 2b, D) since the nearest previous, accept MFC signal ceased, the fixed threshold is used, if being sufficiently low for the output signal from the receiver 17 to exceed level 1, even for the weakest acceptable MFC signal. When an accepted MFC signal ceases, some time may elapse until all transients and eccoes on the li have faded out.
  • the level of these noise signals is in relation to the level of the MFC signal.
  • the calculation of the DFT is started, there is 5 ms interval monitoring for ascertaining that the signal keeps between the .two sig nal-responsive threshold values level 2 and level 3. If the signal is too weak during a 5 ms interval, the calculation of the DFT is begun again. If the signal continues to be weak for a further three 5 ms intervals, release is indicated from the logic circuit 33 via the out put 32. If the signal becomes stronger instead, so that the upper thre hold value is exceeded, the DFT is also calculated anew, and the thres hold values level 2 and level 3 are furthermore updated anew with va ⁇ lues proportional to the signal from the receiver 18.
  • ⁇ HE in the block 27 with a threshold (level 4) which, similar to level 1 is signal depending during a given limited time after an accepted MF signal, thereafter assuming a fixed value again. If the signal falls below level 4, the receiver 18 returns to its resting state. If leve 4 is exceeded, the sum of the selectively calculated energies is com pared in the block 24 with a threshold which is proportional to the output signal squared in the block 25 and coming from the non-selec- tive receiver 18.
  • Figure 2d illustrates the output signal from a se ⁇ lective receiver for a frequency which is included in the input sign It will be seen that signal processing begins at point B and the com parison takes place at point C.
  • Figure 2e illustrates the output sig nal from a selective receiver for a frequency which is not a part of the input signal.
  • the signal is recognized as being caused by some interfe rence and not as an MFC signal. If the energy within the passbands i sufficient, the greatest of the measures of energy from the selective receivers is selected in block 28 as a reference value, and in block 30 all selectively calculated measures of energy are compared with this value and also with a threshold value which is proportional to the greatest signal and which is formed in block 29. If no selectivel calculated energy value exceeds the minimum value, the signal is re ⁇ cognized as a noise signal.
  • An MFC frequency is recognized as being present if the selective receiver for this frequency has an energy measure exceeding the- minimum value and ly.ing within a .given.toleranc range under the reference value.
  • the tolerance is set, in accordance with the CCITT R2 specification, more narrowly for a frequency which lies closer to the frequency with the greatest measure of energy, so that a false operation cannot be caused by a single-tone signal. If one or more than two MFC frequencies are present, time monitoring is started which gives an alarm if incorrect combinations arise during the whole of the monitoring time. If two, and only two, frequencies are present, the two signal-responsive threshold levels 1 and 4 are updated, and after monitoring for a further 5 ms (measured from point C) that the signal remains, the logical output decision (Figure 2f) from the MFC receiver is given concerning the presence of a frequency included in the input signal simultaneously as possible time monitori for alarm ceases (Figure 2f).
  • the -practical embodiment of the apparatus in accordance with the in- vention is based on known digital filter techniques. There is no diffi culty for one skilled in the art to construct a multi-frequency re ⁇ ceiver in accordance with the invention with guidance from the define conditions, and accordingly a more detailed description of the filter or the remaining arithmetical and logical circuits is superfluous.
  • the individual operations multiplication, addition and comparison ca be executed with known components in a known manner. Accumulation can be executed by addition and storing the result in a memory. Time measure ent can be executed by accumulation and comparison.
  • the arith ⁇ metical circuits will however be most efficiently utilized if all -multiplications of signal by signal (squaring) are carried out in one and the same multiplier, which is utilized in time multiplex. Similar ly, all additions and comparisons may be executed in one and the same arithmetical circuit, irrespective of where the operation is carried out in the block diagram.
  • Accumulation of the products of multiplica- tion in the selective receivers and of variables for time measurement storage of sampling values in the non-selective receivers as well as storage of variable thresholds and state variables for the operation and release circuits may be carried out in a common write-and-read memory RWM, while the coeff cients in both the selective and the non selective receivers as well as the coefficients for calculating the threshold values may a'll be stored in a common read memory PROM.
  • the structure for the most- suitable circuit solution for an embodiment will be different, depending on whether merely one arrangment or several arrangements in time multiplex are intended to be realized.
  • the control of the multiplex-utilized multiplier and adder as well as the read operations in the PROM and the write and read operations in the RWM may be obtained from a program memory which is addressed by a counter, while the generation of new values for the state variables can be carried out by combinatorial logical circuits of by using microprocessors.
  • the embodiment according to the described example refers to an appar for identifying signals according to the CCITT specification for a r DCver adapted to the register signalling system R2.
  • the apparatus defined in the patent claims may also be implemented for other frequency systems.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)
  • Noise Elimination (AREA)

Abstract

Un appareil permet d'identifier des signaux à fréquences multiples, les signaux reçus étant traités dans des récepteurs sélectifs (1-6) après leur passage par un filtre numérique de bande passante (7). Le signal d'entrée arrivant dans les récepteurs est multiplié à chaque temps d'échantillonnage par un coéfficient provenant de chacun des deux ensembles de coefficients. Le premier ensemble (8) est obtenu en multipliant une fonction sinus par une fonction de pondération et l'autre ensemble (9) est obtenu en multipliant la même fonction sinus déphasée de pi/2, par la même fonction de pondération. Le produit de la multiplication est accumulé (12, 13) et élevé au carré (14, 15) individuellement pour chacune des multiplications, et les résultats au carré sont additionnés (16) pour obtenir une mesure du signal d'énergie dans la bande passante. Les signaux reçus sont soumis à une génération de quantités absolues et à une filtration numérique dans deux récepteurs non sélectifs (17, 18), dont le premier (17) est affecté par les changements dans le niveau du signal composite d'entrée et commande le début ou départ des périodes de calcul dans le récepteurs sélectifs, et l'autre (18) génère un signal qui est une mesure de l'amplitude de l'enveloppe. Un circuit (23) forme un signal d'addition à partir de tous les récepteurs sélectifs et un circuit de comparaison (24) compare le signal d'addition avec un signal obtenu en élevant au carré le signal de sortie provenant du second récepteur non sélectif (18). Un circuit logique (28) sélectionne le plus grand des signaux provenant des récepteurs sélectifs, un circuit de seuil (29) forme une valeur de seuil qui est proportionnelle à ce plus grand signal, et un circuit de comparaison (30) décide du signal, parmi les signaux restants, qui est suffisamment grand pour indiquer ensemble avec le signal le plus grand, qu'un signal numérique à fréquences multiples a été reçu.
PCT/SE1983/000107 1982-04-06 1983-03-25 Appareil d'identification de signaux numeriques a frequences multiples WO1983003732A1 (fr)

Priority Applications (6)

Application Number Priority Date Filing Date Title
GB08409831A GB2135488B (en) 1982-04-06 1983-03-25 Apparatus for identifying digital multi-frequency signals
NL8320091A NL8320091A (nl) 1982-04-06 1983-03-25 Inrichting voor het identificeren van digitale signalen met een aantal freguenties.
BR8307505A BR8307505A (pt) 1982-04-06 1983-03-25 Aparelho para identificar sinais de multiplas frequencias
AU14757/83A AU1475783A (en) 1982-04-06 1983-03-25 Apparatus for identifying digital multi-frequency signals
DK559683A DK559683A (da) 1982-04-06 1983-12-05 Apparat til at identificere digitale flerfrekvenssignaler
FI841600A FI841600A0 (fi) 1982-04-06 1984-04-24 Anordning foer att identifiera digitala flerfrekvenssignaler.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8202191-6820406 1982-04-06
SE8202191A SE430554B (sv) 1982-04-06 1982-04-06 Anordning for att identifiera digitala flerfrekvenssignaler

Publications (1)

Publication Number Publication Date
WO1983003732A1 true WO1983003732A1 (fr) 1983-10-27

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1983/000107 WO1983003732A1 (fr) 1982-04-06 1983-03-25 Appareil d'identification de signaux numeriques a frequences multiples

Country Status (9)

Country Link
US (1) US4614909A (fr)
ES (1) ES8404130A1 (fr)
FI (1) FI841600A0 (fr)
GB (1) GB2135488B (fr)
IT (1) IT8320471A0 (fr)
NL (1) NL8320091A (fr)
NO (1) NO834469L (fr)
SE (1) SE430554B (fr)
WO (1) WO1983003732A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4759748A (en) * 1986-06-30 1988-07-26 Raychem Corporation Guiding catheter
EP0480260A2 (fr) * 1990-10-12 1992-04-15 Telenorma Gmbh Récepteur multi-fréquences numérique pour central de télécommunications

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3505950A1 (de) * 1985-02-21 1986-08-21 Deutsche Itt Industries Gmbh, 7800 Freiburg Integrierbare schaltungsanordnung zur identifizierung eines pilottones
NL8502008A (nl) * 1985-07-12 1987-02-02 Philips Nv Ontvanginrichting voor het onder bescherming van een stoorsignaal/spraaksignaalbewakingsfunctie herkennen van een aantal verschillende en voorafbepaalde frequentiecombinaties van toonfrequente signaleringscomponenten.
DE3629907A1 (de) * 1986-09-03 1988-03-10 Standard Elektrik Lorenz Ag Signalisierungsempfaenger
US4853958A (en) * 1988-06-02 1989-08-01 Northern Telecom Limited LPC-based DTMF receiver for secondary signalling
WO1990000841A1 (fr) * 1988-07-15 1990-01-25 Luminis Pty. Ltd. Commande de protection et de priorite d'acces en file d'attente repartie
CA2116043C (fr) * 1994-02-21 1997-09-23 Alexander F. Tulai Detecteur de tonalites de progression d'appel numerique programmable
US5793306A (en) * 1995-12-29 1998-08-11 Vershinin; Michael Identification systems employing frequency-based coded information
JPH09243679A (ja) * 1996-03-05 1997-09-19 Takayoshi Hirata 任意区間波形を用いた非調和的周波数分析法
US7317765B2 (en) * 2002-11-26 2008-01-08 The Johns Hopkins University Signal observation system

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875347A (en) * 1973-10-01 1975-04-01 Gte Automatic Electric Lab Inc Multifrequency signal receiver
GB2049360A (en) * 1979-04-24 1980-12-17 Kokusai Denshin Denwa Co Ltd Digital signal processing system

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3935539A (en) * 1974-04-08 1976-01-27 The United States Of America As Represented By The Secretary Of The Navy A-C signal multiplying circuit by a ratio of whole numbers the numerator of which is greater than one and greater than the denominator
US4142177A (en) * 1976-08-12 1979-02-27 Motorola, Inc. Digital tone decoder system
US4145660A (en) * 1977-12-23 1979-03-20 Rca Corporation Frequency activated circuit
US4230991A (en) * 1978-09-11 1980-10-28 Alexandre Paphitis Digital frequency process and method using frequency shifting techniques, especially for low frequency measurements
JPS5830793B2 (ja) * 1978-10-04 1983-07-01 株式会社日立製作所 多周波信号受信方式
NL177552C (nl) * 1979-05-02 1985-10-01 Nederlanden Staat Inrichting voor het onder gebruikmaking van een digitale correlatiemethode vaststellen van de aanwezigheid van elke van een aantal vaste frequenties in een signaal.
CA1137565A (fr) * 1979-05-22 1982-12-14 Masaharu Kawaguchi Recepteur multifrequence numerique
US4368434A (en) * 1980-09-18 1983-01-11 Codex Corporation Programmable digital detector for the demodulation of angle modulated electrical signals
US4399536A (en) * 1981-10-02 1983-08-16 Bell Telephone Laboratories, Incorporated Convolution filter arrangement for digital multifrequency receiver

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875347A (en) * 1973-10-01 1975-04-01 Gte Automatic Electric Lab Inc Multifrequency signal receiver
GB2049360A (en) * 1979-04-24 1980-12-17 Kokusai Denshin Denwa Co Ltd Digital signal processing system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4759748A (en) * 1986-06-30 1988-07-26 Raychem Corporation Guiding catheter
EP0480260A2 (fr) * 1990-10-12 1992-04-15 Telenorma Gmbh Récepteur multi-fréquences numérique pour central de télécommunications
EP0480260A3 (en) * 1990-10-12 1992-07-22 Telenorma Gmbh Digital multifrequency receiver for communication exchange

Also Published As

Publication number Publication date
SE430554B (sv) 1983-11-21
FI841600A (fi) 1984-04-24
FI841600A0 (fi) 1984-04-24
ES521229A0 (es) 1984-04-01
ES8404130A1 (es) 1984-04-01
IT8320471A0 (it) 1983-04-06
NO834469L (no) 1983-12-05
GB2135488A (en) 1984-08-30
GB2135488B (en) 1985-08-07
US4614909A (en) 1986-09-30
GB8409831D0 (en) 1984-05-23
NL8320091A (nl) 1984-07-02
SE8202191L (sv) 1983-10-07

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